6 hotfies, all cc:stable. Some fixes for longstanding nilfs2 issues and

three unrelated MM fixes.
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Merge tag 'mm-hotfixes-stable-2024-07-03-22-23' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull misc fixes from, Andrew Morton:
 "6 hotfies, all cc:stable. Some fixes for longstanding nilfs2 issues
  and three unrelated MM fixes"

* tag 'mm-hotfixes-stable-2024-07-03-22-23' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  nilfs2: fix incorrect inode allocation from reserved inodes
  nilfs2: add missing check for inode numbers on directory entries
  nilfs2: fix inode number range checks
  mm: avoid overflows in dirty throttling logic
  Revert "mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again"
  mm: optimize the redundant loop of mm_update_owner_next()

fs/nilfs2/alloc.c

@@ -377,11 +377,12 @@ void *nilfs_palloc_block_get_entry(const struct inode *inode, __u64 nr,
  * @target: offset number of an entry in the group (start point)
  * @bsize: size in bits
  * @lock: spin lock protecting @bitmap
+ * @wrap: whether to wrap around
  */
 static int nilfs_palloc_find_available_slot(unsigned char *bitmap,
 					    unsigned long target,
 					    unsigned int bsize,
-					    spinlock_t *lock)
+					    spinlock_t *lock, bool wrap)
 {
 	int pos, end = bsize;
 
@@ -397,6 +398,8 @@ static int nilfs_palloc_find_available_slot(unsigned char *bitmap,
 
 		end = target;
 	}
+	if (!wrap)
+		return -ENOSPC;
 
 	/* wrap around */
 	for (pos = 0; pos < end; pos++) {
@@ -495,9 +498,10 @@ int nilfs_palloc_count_max_entries(struct inode *inode, u64 nused, u64 *nmaxp)
  * nilfs_palloc_prepare_alloc_entry - prepare to allocate a persistent object
  * @inode: inode of metadata file using this allocator
  * @req: nilfs_palloc_req structure exchanged for the allocation
+ * @wrap: whether to wrap around
  */
 int nilfs_palloc_prepare_alloc_entry(struct inode *inode,
-				     struct nilfs_palloc_req *req)
+				     struct nilfs_palloc_req *req, bool wrap)
 {
 	struct buffer_head *desc_bh, *bitmap_bh;
 	struct nilfs_palloc_group_desc *desc;
@@ -516,7 +520,7 @@ int nilfs_palloc_prepare_alloc_entry(struct inode *inode,
 	entries_per_group = nilfs_palloc_entries_per_group(inode);
 
 	for (i = 0; i < ngroups; i += n) {
-		if (group >= ngroups) {
+		if (group >= ngroups && wrap) {
 			/* wrap around */
 			group = 0;
 			maxgroup = nilfs_palloc_group(inode, req->pr_entry_nr,
@@ -550,7 +554,14 @@ int nilfs_palloc_prepare_alloc_entry(struct inode *inode,
 			bitmap_kaddr = kmap_local_page(bitmap_bh->b_page);
 			bitmap = bitmap_kaddr + bh_offset(bitmap_bh);
 			pos = nilfs_palloc_find_available_slot(
-				bitmap, group_offset, entries_per_group, lock);
+				bitmap, group_offset, entries_per_group, lock,
+				wrap);
+			/*
+			 * Since the search for a free slot in the second and
+			 * subsequent bitmap blocks always starts from the
+			 * beginning, the wrap flag only has an effect on the
+			 * first search.
+			 */
 			kunmap_local(bitmap_kaddr);
 			if (pos >= 0)
 				goto found;

fs/nilfs2/alloc.h

@@ -50,8 +50,8 @@ struct nilfs_palloc_req {
 	struct buffer_head *pr_entry_bh;
 };
 
-int nilfs_palloc_prepare_alloc_entry(struct inode *,
-				     struct nilfs_palloc_req *);
+int nilfs_palloc_prepare_alloc_entry(struct inode *inode,
+				     struct nilfs_palloc_req *req, bool wrap);
 void nilfs_palloc_commit_alloc_entry(struct inode *,
 				     struct nilfs_palloc_req *);
 void nilfs_palloc_abort_alloc_entry(struct inode *, struct nilfs_palloc_req *);

fs/nilfs2/dat.c

@@ -75,7 +75,7 @@ int nilfs_dat_prepare_alloc(struct inode *dat, struct nilfs_palloc_req *req)
 {
 	int ret;
 
-	ret = nilfs_palloc_prepare_alloc_entry(dat, req);
+	ret = nilfs_palloc_prepare_alloc_entry(dat, req, true);
 	if (ret < 0)
 		return ret;
 

fs/nilfs2/dir.c

@@ -135,6 +135,9 @@ static bool nilfs_check_folio(struct folio *folio, char *kaddr)
 			goto Enamelen;
 		if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))
 			goto Espan;
+		if (unlikely(p->inode &&
+			     NILFS_PRIVATE_INODE(le64_to_cpu(p->inode))))
+			goto Einumber;
 	}
 	if (offs != limit)
 		goto Eend;
@@ -160,6 +163,9 @@ static bool nilfs_check_folio(struct folio *folio, char *kaddr)
 	goto bad_entry;
 Espan:
 	error = "directory entry across blocks";
+	goto bad_entry;
+Einumber:
+	error = "disallowed inode number";
 bad_entry:
 	nilfs_error(sb,
 		    "bad entry in directory #%lu: %s - offset=%lu, inode=%lu, rec_len=%zd, name_len=%d",

fs/nilfs2/ifile.c

@@ -56,13 +56,10 @@ int nilfs_ifile_create_inode(struct inode *ifile, ino_t *out_ino,
 	struct nilfs_palloc_req req;
 	int ret;
 
-	req.pr_entry_nr = 0;  /*
-			       * 0 says find free inode from beginning
-			       * of a group. dull code!!
-			       */
+	req.pr_entry_nr = NILFS_FIRST_INO(ifile->i_sb);
 	req.pr_entry_bh = NULL;
 
-	ret = nilfs_palloc_prepare_alloc_entry(ifile, &req);
+	ret = nilfs_palloc_prepare_alloc_entry(ifile, &req, false);
 	if (!ret) {
 		ret = nilfs_palloc_get_entry_block(ifile, req.pr_entry_nr, 1,
 						   &req.pr_entry_bh);

fs/nilfs2/nilfs.h

@@ -116,9 +116,15 @@ enum {
 #define NILFS_FIRST_INO(sb) (((struct the_nilfs *)sb->s_fs_info)->ns_first_ino)
 
 #define NILFS_MDT_INODE(sb, ino) \
-	((ino) < NILFS_FIRST_INO(sb) && (NILFS_MDT_INO_BITS & BIT(ino)))
+	((ino) < NILFS_USER_INO && (NILFS_MDT_INO_BITS & BIT(ino)))
 #define NILFS_VALID_INODE(sb, ino) \
-	((ino) >= NILFS_FIRST_INO(sb) || (NILFS_SYS_INO_BITS & BIT(ino)))
+	((ino) >= NILFS_FIRST_INO(sb) ||				\
+	 ((ino) < NILFS_USER_INO && (NILFS_SYS_INO_BITS & BIT(ino))))
+
+#define NILFS_PRIVATE_INODE(ino) ({					\
+	ino_t __ino = (ino);						\
+	((__ino) < NILFS_USER_INO && (__ino) != NILFS_ROOT_INO &&	\
+	 (__ino) != NILFS_SKETCH_INO); })
 
 /**
  * struct nilfs_transaction_info: context information for synchronization

fs/nilfs2/the_nilfs.c

@@ -452,6 +452,12 @@ static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
 	}
 
 	nilfs->ns_first_ino = le32_to_cpu(sbp->s_first_ino);
+	if (nilfs->ns_first_ino < NILFS_USER_INO) {
+		nilfs_err(nilfs->ns_sb,
+			  "too small lower limit for non-reserved inode numbers: %u",
+			  nilfs->ns_first_ino);
+		return -EINVAL;
+	}
 
 	nilfs->ns_blocks_per_segment = le32_to_cpu(sbp->s_blocks_per_segment);
 	if (nilfs->ns_blocks_per_segment < NILFS_SEG_MIN_BLOCKS) {

fs/nilfs2/the_nilfs.h

@@ -182,7 +182,7 @@ struct the_nilfs {
 	unsigned long		ns_nrsvsegs;
 	unsigned long		ns_first_data_block;
 	int			ns_inode_size;
-	int			ns_first_ino;
+	unsigned int		ns_first_ino;
 	u32			ns_crc_seed;
 
 	/* /sys/fs/<nilfs>/<device> */

kernel/exit.c

@@ -484,6 +484,8 @@ void mm_update_next_owner(struct mm_struct *mm)
 	 * Search through everything else, we should not get here often.
 	 */
 	for_each_process(g) {
+		if (atomic_read(&mm->mm_users) <= 1)
+			break;
 		if (g->flags & PF_KTHREAD)
 			continue;
 		for_each_thread(g, c) {

mm/page-writeback.c

@@ -415,13 +415,20 @@ static void domain_dirty_limits(struct dirty_throttle_control *dtc)
 	else
 		bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE;
 
-	if (bg_thresh >= thresh)
-		bg_thresh = thresh / 2;
 	tsk = current;
 	if (rt_task(tsk)) {
 		bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32;
 		thresh += thresh / 4 + global_wb_domain.dirty_limit / 32;
 	}
+	/*
+	 * Dirty throttling logic assumes the limits in page units fit into
+	 * 32-bits. This gives 16TB dirty limits max which is hopefully enough.
+	 */
+	if (thresh > UINT_MAX)
+		thresh = UINT_MAX;
+	/* This makes sure bg_thresh is within 32-bits as well */
+	if (bg_thresh >= thresh)
+		bg_thresh = thresh / 2;
 	dtc->thresh = thresh;
 	dtc->bg_thresh = bg_thresh;
 
@@ -471,7 +478,11 @@ static unsigned long node_dirty_limit(struct pglist_data *pgdat)
 	if (rt_task(tsk))
 		dirty += dirty / 4;
 
-	return dirty;
+	/*
+	 * Dirty throttling logic assumes the limits in page units fit into
+	 * 32-bits. This gives 16TB dirty limits max which is hopefully enough.
+	 */
+	return min_t(unsigned long, dirty, UINT_MAX);
 }
 
 /**
@@ -508,10 +519,17 @@ static int dirty_background_bytes_handler(struct ctl_table *table, int write,
 		void *buffer, size_t *lenp, loff_t *ppos)
 {
 	int ret;
+	unsigned long old_bytes = dirty_background_bytes;
 
 	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
-	if (ret == 0 && write)
+	if (ret == 0 && write) {
+		if (DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE) >
+								UINT_MAX) {
+			dirty_background_bytes = old_bytes;
+			return -ERANGE;
+		}
 		dirty_background_ratio = 0;
+	}
 	return ret;
 }
 
@@ -537,6 +555,10 @@ static int dirty_bytes_handler(struct ctl_table *table, int write,
 
 	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 	if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
+		if (DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) > UINT_MAX) {
+			vm_dirty_bytes = old_bytes;
+			return -ERANGE;
+		}
 		writeback_set_ratelimit();
 		vm_dirty_ratio = 0;
 	}
@@ -1660,7 +1682,7 @@ static inline void wb_dirty_limits(struct dirty_throttle_control *dtc)
 	 */
 	dtc->wb_thresh = __wb_calc_thresh(dtc, dtc->thresh);
 	dtc->wb_bg_thresh = dtc->thresh ?
-		div64_u64(dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0;
+		div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0;
 
 	/*
 	 * In order to avoid the stacked BDI deadlock we need